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Old 08-31-2021, 12:19 PM   #1
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Maybe another dumb? Battery question

Ran fridge 2 days before,unplugged light,stuffed it full. Drove 5 hours,fired up lp,set up camp. Battery 100% (didn't wait 3 hrs to test tho). 14hrs later battery is 70%. Ran genny 2hrs in am, 3hrs pm. 14hrs bat is 60%. Basically each day lost 10,so I would run it hrs longer(park was EMPTY !).
BATTERY IS 140amp DEEP.
Question is this; if I had 2 would I likely finish last 10% charge ?
My unit is a dp 4045 and gunny is sportsman 2000i Ran it on economy most of time but it does speed up if power is called for.
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Old 08-31-2021, 02:29 PM   #2
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I think your ultimate question is will adding a second generator improve your battery charge rate, Nope!

Sounds like you have a 2 way gas/electric refrigerator.

How long a battery lasts, depends on a few things; 1st your camping style, 2nd, battery condition.

Running the frig on gas, takes very little power. I can camp two days without much issue on my 104 amp/hr battery. There are lots of parasite power drains on the battery. Don't forget all the lights and slides, awnings, inverters, etc can pull down a battery fairly quickly. Also do you use a CPAP? If so, they can pull a lot of power, especially if you have the humidifier and heat options turned on.

How did you test your battery charge? did you use the battery monitor button on your control panel? A few lite up a few LEDs on a bar really does not give you any real information. Multimeter is much better tool. There are charts you can cross reference, voltage reading to 90% capacity.

As for charging the battery the last 5-10% is what takes a lot of time. It is also what gives back the most charge when you need it. Many people's goals is to reach the 90% rate each evening after turning off the genny. It really just comes down to, the batteries need time to soak up the last of the power. More generator will not charge the battery any faster. The genny only provides as much power as the camper is asking for (hence the speed up when needed). If the camper wants more power than what the genny can provide, it will trip the overload circuit on the genny.

When boondocking and running the genny, I tend to run an hour or two in the morning and again in the evening. If I need more than that, I would look at why. Might be camping style. Run a lots of electronics, lights are left on in areas you are not using (walk outside and leave every light on???), invertor is left on when not needed. What is the battery condition? How old is it? Is it a lead acid wet cell? Has the water level in cells been checked? How often is distilled water being added to the cells? FYI, only add DISTILLED water to a wet cell battery, anything else will shorten the battery life.
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Old 08-31-2021, 02:48 PM   #3
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Jaygiven, no it's WILL A SECOND BATTERY. GENNY IS 2200/1800 WATT.
#1, NO LIGHTS,etc. Only fridge on gas and stuff I can't kill
(radio,usb,detectors). New battery,full and digital led meter.
My point about genny was that it does put out enough (45 amps available)
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Old 09-02-2021, 12:04 PM   #4
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Ran fridge 2 days before,unplugged light,stuffed it full. Drove 5 hours,fired up lp,set up camp. Battery 100% (didn't wait 3 hrs to test tho). 14hrs later battery is 70%. Ran genny 2hrs in am, 3hrs pm. 14hrs bat is 60%. Basically each day lost 10,so I would run it hrs longer(park was EMPTY !).
BATTERY IS 140amp DEEP.
Question is this; if I had 2 would I likely finish last 10% charge ?
My unit is a dp 4045 and gunny is sportsman 2000i Ran it on economy most of time but it does speed up if power is called for.
What type of camping you do will determine which type and how many batteries. If you do a lot of dry camping don't waist your money on lead acid type batteries. You can now get lithium for not much more if you shop around. Lighter, safer, no off gassing, can be charged faster, and double the amps for same size battery. No brainer in my books
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Old 09-02-2021, 12:44 PM   #5
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Bill, no plan to dry camp,at least often. Family thing in state park. Bought a 140 amp deep cycle. I was asking this, charging a battery down 40% takes 6 hrs vs 20% takes ???
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Old 09-02-2021, 01:38 PM   #6
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A lithium battery takes 2-3 hours for a completely discharged 100 a/hr Most will take a 50 amp charge. Your lucky if lead acid will take half that and then you have to float them forever to get the last 10%. Your 140a/hr only has 70 usable
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Old 09-02-2021, 02:53 PM   #7
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"Question is this; if I had 2 would I likely finish last 10% charge ?"

No, a lead acid battery will always taper the charge as it gets closer to 100% charged. Two batteries will give you more usage amps (time) but will not speed up the charge and for most chargers, will actually take a longer time to charge to 80~90% and the last 10% will not be any faster. The point Bill is making (in part) is that a lifepo4 battery can take a faster charge than a lead acid battery, therefore reducing the generator (charger) run time. ~CA
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Old 09-02-2021, 02:54 PM   #8
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It says 83 amps I think. So is 10% based on battery amps or charge needed ? On 140 amps, it's 14 amps or I used 20 amps so it's 2 ? I built computers for people and wired homes from service to plugs and this battery stuff escapes me
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Old 09-02-2021, 03:14 PM   #9
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The State Of Charge (SOC) is based on its capacity, so as you stated if it was at 90% then the other 10% would represent 14 amps on a 140ah battery. However the 10% (or any percent) is simply an estimate based on the batteries voltage which is what the charging circuit uses to lower the current (charge rate) as the battery gets close to fully charged. When you see a charger that has options for AGM, Gel, lead acid, etc, (if you are using your RV converter then it is set for Lead Acid most likely and may not have any choices for other battery types), anyway, the difference in each choice is to tell the charger at what voltage to start tapering and what voltage is a full charge. Where are you reading the 10% value from? ~CA
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Old 09-02-2021, 03:43 PM   #10
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I might be re-iterating, but oh well..
For lead acid you can only use 50% of your amp hours before you damage the battery cells and it holds less amp hours. The lower below 50% the more damage the less the battery can hold at 100% charge. As mentioned, 140amp/hr at 50% is 70amp/hr. If you have ever gone below 70, damage has occurred and you can no longer reach 140amp/hr. Given age of battery this may be true as well. Lead acid last 3-4 years when treated well.

Let's say the battery is new/has been treated well and you can charge to 140amp/hr. When you are at 80amp/hr and run genny, it will start with a high current to charge fast. The closer to 140amp/hr (full charge) the lower the current. To get from 80-100amp/hr might take 45min (guessing - numbers just for understanding how it works), to get from 100amp/hr to 120 might take 2hrs as the charger decreases current to make sure it doesn't cook/boil the battery - charge too fast and doesn't over charge, slow and steady. To get from 120-130 another 3hrs and so on. The closer to 100% charge, the less current is given to the battery, the longer it takes to charge.

Another battery would probably fix the issue as you could charge at a high amp rate longer (charging two batteries at once) to give you a total battery charge higher. IE one battery high amp charge gets you to 100amp/hrs, but if you had two batteries the high amp charge may get you to 200amp/hrs, thus giving you enough power for the next day. The addition of a second battery allows you to increase the high amp charge time which should give you a total amp hour charge higher with two batteries.
140amp/hr battery high current up to 80% full = 112amp/hr
280amp/hr batteries high current charge up to 80% full = 224amp/hr

Just remember you need to replace all batteries at once and not just one at a time. The old battery will bring down the new one and make it burn out faster.
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Old 09-02-2021, 05:27 PM   #11
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Craig, just hypothetical. While camping I checked voltage with digital meter. After charging 3 hrs, wait 3hrs and check voltage.
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Old 09-02-2021, 05:32 PM   #12
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Mini, thanks . Kinda what I was asking . 1 battery 30% down,charge 4hrs to 90%, 2 batteries each 15% down maybe 2hrs to charge more time to get last 10%
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Old 09-03-2021, 09:00 AM   #13
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Your charger may not charge at a rate that would charge two batteries faster, would have to check the charging output specs. of your charger
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Old 09-03-2021, 09:47 AM   #14
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I wanted to do a little more research and found a few articles that are more helpful. When ever you deal with power, there's never a simple answer which is why you have so many opinions/experiences. How you use it, where you are (outside conditions) and hardware capability (battery, charger, power source) all play into the equation.

Hopefully I'm not making this too complicated.. but also trying to make sure you have good information to make a decision.

Good read:
https://batteryuniversity.com/articl...ging-lead-acid
https://www.mastervolt.com/charging-batteries/

More facts:
Max charge rate (amps) for lead acid is 25% of amp/hour
140amp/hr / 4 = 35amp max charge rate
280amp/hr /4 = 70amp max charge rate (two batteries in series)
The 25% number prevents boiling, oxidation leading to battery damage.

Lead Acid should be charged with a multi-stage charger. This allows for higher current charge at lower SOC and then when 80% hits, it can lower the charge to more evenly charge all the cells to 90-95% and then move to a float charge (trickle charge) to reach 100%

You mentioned having a sportsman 2000i genny; I didn't find the 'i' model, but the 2000 specs are:
running watts 1400W = 120v*11.7 amps
starting watts 2000W = 120v*16.6 amps
you mention 2200/1800 in a post which would be
running watts 1800W = 120v*15 amps
starting watts 2200W = 120v*18.3 amps

So your genny can charge at a max of 11.7amps of constant load and handle a quick hit of 16.6 amps (or 15/18.3 amps depending on genny model)

Two batteries better than one is also determined by the converter/battery charger in the RV, assuming RV is plugged into genny and RV converter is charging the battery. If you have a separate battery charger plugged into the genny and this charger connected to the RV battery, the numbers below apply to the battery charger. In order to charge two batteries at the same rate as one, the battery charger (RV converter or external charger) needs to be able to charge at twice the amperage of one up to the 80% SOC. In your example, 280amp/hr would need to charge at 70amps, very high..

If the battery charger has a max amperage of 30amps, two batteries will charge at the same rate as one and you will see no difference in the total power stored from the generator. If you can charge at a higher amperage rate, you can store more power while the genny is running than a single battery could.

I've seen mostly Progressive Dynamics chargers in posts. I'd look up your model and see what the max amp is on a charge. If its not more than 35amps you can't charge two batteries any faster than one. You can store more power with two batteries, but you'd have a negative balance every day as you can't charge two batteries faster than one.

Progressive Dynamics max output example:
Maximum Output & Charging Rate 9200 Series Model 9100 Series Model
30-amps PD9130
40-amps PD9140A
45-amps PD9245C PD9145A
60-amps PD9260C PD9160A
70-amps PD9270 PD9170
80-amps PD9280 PD9180

I didn't see what SOC% you were at after running the genny for several hours. If the battery got over 80% then the charger would have dropped amperage and started charging slower. In this case, two batteries would help as you can charge at a higher amperage longer. If it did not reach 80%, the genny was not running long enough to charge up to 80% because the genny can't generate enough amperage.

The genny is the current weakest link with max output of 12amps. It can not create enough power to maximize amps charging a single battery is capable of taking (35amps) or most likely what the battery charger is capable of sending. So you either have to run the genny longer to reach 80% OR if you did reach 80%, add a battery to charge at a higher current and store more amp hours.

If you had more charging power your next limit may be the battery charger. You'd have to look up the model and see the max amps it can charge at. If the battery charger max amps is over 25% of the amp hours of the battery, then adding another battery would be helpful (assuming you can generate the additional power)
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Old 09-03-2021, 10:01 AM   #15
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"The genny is the current weakest link with max output of 12amps. It can not create enough power to maximize amps charging a single battery is capable of taking (35amps) or most likely what the battery charger is capable of sending."

Keep in mind that 12 amps @120v is 120 amps @ 12v with a large enough converter\charger (not including the voltage conversion efficiency loss). For example, a 100a charger will pull just a little more than 10a of 120v current (maybe 11~12a @ 120v).
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Old 09-03-2021, 10:51 AM   #16
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Bill, it's a DP 4045. Plenty
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Old 09-03-2021, 11:07 AM   #17
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Mini, it's a PD4045. FROM THE MANUAL.
DC Section Converter Section
Input: 105-130 VAC 50/60 Hz
725 Watts
Output: 13.6 VDC,
45 Amps
Weight: 5.70 lbs
This is genny I can't find ANY info about on board charger. So I plug into it,let pd charge it. Website says 26, 33 surge amps.
https://www.tractorsupply.com/tsc/pr...rator-gen2000i
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Old 09-03-2021, 11:46 AM   #18
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Mini, it's a PD4045. FROM THE MANUAL.
DC Section Converter Section
Input: 105-130 VAC 50/60 Hz
725 Watts
Output: 13.6 VDC,
45 Amps
Weight: 5.70 lbs
This is genny I can't find ANY info about on board charger. So I plug into it,let pd charge it. Website says 26, 33 surge amps.
https://www.tractorsupply.com/tsc/pr...rator-gen2000i
Your generator is similar to many models such as the Powermate 2200I that I own, which puts out ~8 amps at the 12v charger outlet which is not much, but is better than nothing when\if needed and for emergency battery charging. The primary charge you will get is from plugging in the RV and the converters 45a output. However, keep in mind that with 45a output you will most often not get that amperage to the battery(s) as any lights, detectors, fridge, fans, etc., will come out of the 45a so on average I suspect you could get 35a out of it to the battery.

I am still not sure what you would like to change, adding another battery will add more 12v power for a longer period of time, but will not charge "faster" than one battery as each battery will take a similar amount of time to charge if enough amps were available. Keep in mind though that if you only have ~35a available to charge with, then two batteries would split that at ~17.5a per battery which is not a bad thing as far as the battery's longevity (slower and deeper charges are better) but you will not get a faster charge. ~CA
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Old 09-03-2021, 12:30 PM   #19
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Thanks Craig. 8amps from genny, didn't know. I was told it just puts out voltage but not a 2 stage .
My question was if I only have 5hrs to charge, will bringing 1 140amp battery up from 30% down (12.2) to 90% vs 2 at 280amp 15% down (12.35) to closer to 100% in those 5hrs.
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Old 09-07-2021, 09:51 AM   #20
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Nice catch on 120v to 12v changing the amperage. I missed that..

Just to bring it up again, if you discharge a lead acid or AGM battery more than 50%, you start damaging the battery and it will not hold a full charge anymore. In my experience it also seems to discharge faster, but perhaps that's because it never fully charged. The lower below 50% you go, the more damage is done. So when you say charging from 30% back to 100%, its impossible and the battery will never reach 100% SOC. The more you do it, the more damage is done, the farther from 100% you can reach.

If you have a multi stage charger/converter in the RV, which I assume you do since its a relatively new model, you have 3 charging modes.
Bulk/Boost - SOC under 80-90%, charge at high amp rate
Normal/Absorption SOC under 20-10% charge at a low amp
Storage/Float/Trickle - minimal amp rate to keep battery charged

I don't believe there is intelligence in an RV converter/charger to know how many batteries are in parallel and proper max amperage rate. They are most likely designed to operate at maximum based on input power. If your converter can only charge at 30amps and the genny is pushing that max, adding another battery will only double the amount of time it takes to charge. Adding another battery will only give you more power to store/use. New batteries kept above 50%SOC will prevent damage and store more power to use.
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