Crown 935amh 24volt battery

System · October 2007

My Trojan L16's are going south at the count of 1 or 2 every 3 months. After a period of misuse when I was gone for 6 months last summer (didn't get watered, lesson learned....can't trust friends to do this for you) They are now 5 years old (batteries not friends). I want to put the Crown 24Volt forklift battery in. I have 10 120 watt panels. Question is do i have enough power to keep this monster charged? I hadn't had to run the genny in 3 years with this setup (16 Trojans). What do you guys think? I'd like to put 2 Crowns in, is that really pushing it?

Thanks
Gene

BB. · October 2007

Re: Crown 935amh 24volt battery

Not the battery expert here... What is the Battery system voltage and amp*hours of your system (current and proposed new)...

Is not your L16 bank something like 900 AH (at 24 VDC) too. Those 16x L16 batteries are virtually the same capacity as the one Crown battery you are proposing.

The normal rule of thumb is, roughly solar panels for 3% to 10%+ of battery capacity is a good range to be in...

1,200 watts panels/(935a*24volts) = 5.3% panel/battery capacity.

Two banks of Crown batteries would be a bit much for this system (may take too long to recharge the batteries and cause premature aging).

If you have not been running a generator for three years, I would not suggest that you over size the battery bank. Batteries do age and if you battery bank is sufficient for normal use (say three days of no sun with normal loads to 50% discharge), then oversizing the battery bank will not add much except more cells to check and more costs (probably better to buy two batteries 10 years apart than to buy a set of two that last 10-15 years, then buy another two).

If you don't have one, a good battery monitor would also be a nice addition to your system to manage the battery's state of change (as well as a good temperature compensated hydrometer).

-Bill

niel · October 2007

Re: Crown 935amh 24volt battery

i agree with bill that you can have the crowns at 935ah and it would be a decent match. the only way you could double up on it would be to switch between battery banks so that one is charging while the other is being used. the only other ways around it would to either double your pv capacity or get and ac charger that can handle the extra load.

System2 · October 2007

Re: Crown 935amh 24volt battery

Bill and Neil,
Thanks for your response. Originally I had 16 Trojan's 350amh each total 1400amh. It's a 24 volt system with the Trace SW4024 inverter. 10 24volt 120watt panels mounted on 2 poles that I move manually throughout the day. The only time I ran the genny in the past 5 1/2 years is when the battery bank reach a 20% discharge. Even at that the sun came out the next day and I would have been fine. I've never taken them down past 20%. But I really don't know what happened when I was gone for 6 months last summer! When I got back my water pump wouldn't even start. I had 3 batteries with a dead cell each. I deleted one of the 4 strings leaving me with one extra good battery which I used 3 months ago to replace another one that went bad. I get along fine with the remaining 3 strings. I really think I could have gotten 10+ years out of these batteries. I've been watching the Specific Gravity closely and it is droping in all cells steadly. I want to retire the remaining 'good' Trojans and put one Crown in. Am I correct in assuming I can safely go 25 to 30% discharge with the Crown without any big effect on overall battery life? At 25% I'd be even better than at 20% with the Trojans. What concerned me is the info on the AZ Wind & Sun web site saying to use the big Crown I need 40 to 80 amps to keep them charged. At full sun I get easily 34 to 38 amps and sometimes as much as 50 with the right cloud condition. It did seam to me I could run one of the crowns and 2 would be maby too much. Bill, your formula seams to be rite on. Thanks again foir the feedback.
Gene

BB. · October 2007

Re: Crown 935amh 24volt battery

I will let others go into the details of 20 vs 25% discharge levels as I am not the battery expert... But from what I have read and seen, I don't think that you will materially affect the life of the battery with that little bit of "extra" deep discharge.

Wind Sun is recommending that they need 40-80 amps for equalization about once per month... At 34-38 amps, you are probably more than close enough to properly equalize--but it would not hurt to ask Wind Sun about their recommendations. If you can grab one of Wind-Sun's old stock of Crown batteries and save $800, you could use the savings for an extra couple solar panels or other support equipment.

You have the rest of the system setup appropriately--battery temperature probe for the charge controller--and you may wish to use a battery monitor rather than use a hydrometer too often to watch your state of charge...

It is possible that constant use (or "over use" of the hydrometer has caused issues (loss of electrolyte from every reading or cell contamination) and could have helped caused cells to die prematurely--sounds like you are very careful, so this was probably not your issue--but it is always a possibility.

-Bill

PS: Niel's suggestion of using a battery isolator switch would be a good idea to separate the two Crown banks so that you can properly equalize each one individually--but, at your current usage levels, I still would suggest that you purchase only one battery unless you see your power usage doubling (or more) in the next few years--and even then, you should probably up your solar panel count too at that point to keep up with the usage.

System2 · October 2007

Re: Crown 935amh 24volt battery

Bill,

I didn't mention but I do use the Link 10 battery monitor which I find far superior to the Trace that I use in other installs. I may go with the Outback panel controller instead of more panels. I installed one of those a while back and am impressed with it. I just dred re-wiring my panels. I do use the temp. probe with the Trace inverter.

thanks again!
Gene

Crown 935amh 24volt battery

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