Quote:
Originally Posted by jdux999
Hello All. I want to add a second battery to my Redhawk 26 XD. The current battery is a Harris 27D170 with a reserve capacity of 160. Best I can figure, a RC of 160 is approximately 80 Amp Hours. If I add a second battery, that's the equivalent of what I already have, what should I be looking for if the ratings are in Amp Hours? Thanks for the help.
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The first answer is that when you add a 2nd battery to your existing one it needs to be the exact same battery. IE.. same mfr, same Ah's and about the same age. But before you go out and spend money on an exact replacement you need to answer a few questions:
- How old is the existing battery? Age also reduces the battery output. If there is an age difference of 6 months or more, your money would be better spent on replacing both batteries, as the new battery will be brought down to the performance of the older batter which means a shorter life. The internal resistance of the 2 batteries will not be the same, which means different charging/discharging characteristics.
- Has your existing battery voltage been discharged to 10.5 volts (actual dead 12volt battery) or lower... see the above response as you have no idea as to what damage was done to the cells of the existing battery. Buy 2 new batteries.
- Has your existing battery been discharged to just about no voltage.. see the above response
- Have you had to keep adding water to the existing battery over time? Possible cell problem.... see above response
- Have any of the battery plates been exposed to air (low water level)… you got it, see the above response
A battery that has had any of the above things happen to it may charge properly and hold a charge like any other battery, but the difference will be apparent in the Ah's (how long your battery will last under loads). Each of the above issues will lower the amount of Ah's that your battery has to offer.
Personally if any of the above things have happened, yes buy 2 new batteries. No reason to shorten the life of your new battery and throw away your hard earned $$$.
Here is a
battery test (shows what aging or ageing, which ever you prefer, does to batteries) that I did on my old Interstate batteries which I replaced with 2 (6 volt) TROJAN T145, 260Ah batteries. The test results were that I had a substantial drop in Ah's but charging and sitting, the readings were just like a new battery, until you put loads on them.
Below is the proper way of hooking 2 12Volt batteries in parallel to get the best performance out of them. Ignore the cutoff switch if you are not installing one, if you are it can be mounted on either cable Positive or Negative.
Don
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