Battery replacements

[Regalwolf]

I thought I would start a new post with this battery question instead of adding on to the other thread. I have three batteries on the 402 with 315 HP Cummins diesels. I replaced one of the batteries last year (the oldest one died after 7 years). The other two are now about 5 years old. They are fine right now but can't last forever. When I replaced the one last year, I was told they were all gel batteries and I had to replace with a gel battery (he said they can't be mixed); they are 8D gel batteries. The replacement battery was VERY expensive, like around $450 if I recall. In hindsight, I think I should have replaced all three with something less expensive.

So, here are the questions:
1. For diesels, do I need batteries as large as 8Ds?
2. Is there really a problem with mixing gel and non-gel batteries; if so, what is the problem?

Thanks
Frank

[folieadeux]

Frank

1. Your 8D is probably your "house" battery. Your starting batteries should only need to be a group 31 or so (that is the set up I have on my 380 Cummins).

2. If you only have a single battery charger, it is not suggested to mix the different types of batteries since the recharging is different.

[Chris_in_Texas]

As for the mixing of the batteries the issue is charging profiles, if you have a three bank charger you can only select one battery type, so they would all have to be the same. Gel are very sensitive to charging voltage. Everything needs to be setup correctly for gel cells; alternator regulator and battery chargers. The voltage profile is lower than standard AGM/Flooded cells. In theory the Gel can tolerate heat a bit better, but personally I don't think they are worth the cost.

AGM would be a much better solution now a days than gel cells, and are able to tolerate much more abuse than Gels.

As for the engine size I would think that 4D or two group 31 in parallel would be more than sufficient for the "starting" batteries for the engines. The 8D or even some golf cart batteries to replace the 8D are a good way to go for the house bank.

It really comes down to maintenance issues. If the batteries are accessible checking fluid levels is simple enough on flooded cells and those would be your best cost / Ah. Then if you don't want to mess with that, AGM would by my next recommendation, brands like Lifeline are very well respected in the marine industry, and a lot of the manufactures use them in the boats.

[Regalwolf]

Thank you both - very helpful. It looks like I am stuck with the GELs unless I replace all three at the same time with AGM. I do believe all three are 8Ds but will check next time. I will check on 4D gel for the other two batteries when needed - it looks like they are about $100/ea less expensive.

Thanks
Frank