Cruisers Forum

Join CruisersForum Today

  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
Thread Tools Search this Thread Rate Thread Display Modes
Old 02-04-2018, 18:24   #1
Registered User

Join Date: Jan 2017
Location: Irish Sea
Posts: 1,235
Images: 6
Old and new lead batteries in a bank?

Often heard that a single dead battery can kill the entire bank. Is there a way (balancer?) to keep older batteries, still in good condition, without paying with the life of the newer ones?

Useful as a fireproof bottom paint...
GTom is offline   Reply With Quote
Old 02-04-2018, 18:32   #2
Marine Service Provider

Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 1,498
Re: Old and new lead batteries in a bank?

Yes there are battery balancers. We have one that keeps them balanced volts wise but as to effect on life I'll leave to an expert to comment.

Compass790 is online now   Reply With Quote
Old 02-04-2018, 20:27   #3

Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,304
Re: Old and new lead batteries in a bank?

Well "in the same bank" means used concurrently, which is what causes the weakest link to determine the health of the whole.

Keep the old ones in a separate bank, only connected while charging, and use a bank 1-2 switch (no Both) to feed your consumer loads.

Or recycle as Starters?

Not a great idea IMO, just sell off or scrap the older ones.
john61ct is offline   Reply With Quote
Old 04-04-2018, 16:05   #4
Registered User
GrowleyMonster's Avatar

Join Date: Dec 2012
Location: New Orleans
Boat: Bruce Roberts 44 Ofshore
Posts: 2,263
Re: Old and new lead batteries in a bank?

Mixing old and new in parallel without some sort of BMS is a pretty bad idea. Mixing a new one into a series bank is not quite so bad. If you have a 12v system and use 12v batteries in parallel, then I recommend you don't use them in parallel. Connect them as two separate banks with an A/B switch is what I would do.

I have a 48v bank for propulsion, made up of 6v golf cart batteries in series. A year after installing, a "helper" drilled through the cover we were making and into the case of one battery. I tried plugging but the battery went bad and I replaced it with not only a different month, but a different brand. Careful monitoring has detected no problem. So far. SG matches, no load voltage matches. and even individually charging them with a 6v charger shows similar charge current and times. After discharging to 60% or 50% the readings are very consistent among the batteries. YMMV but careful matching can be okay in a series string if they aren't TOO dissimilar in age. 3 years later, still no problems.

Batteries of unequal performance in parallel can be a problem because all current can pass through just one battery. This can overheat the battery, leading to premature failure of the "good" battery. With FLA it is usually not a catastrophe. With some other types things can get noisy.

With FLA, one big bank is somewhat more efficient than two separate banks, due to Peukert effect. Peukert gives you more discharge capacity than the 20 hour rate capacity, at current below the 20 hour discharge rate. Less, at higher discharge current. So you get more bang for the buck by having a higher capacity bank, and one way this is done is to wire batteries in parallel. I'm not saying don't do this, but I am saying don't do this with a mix of batteries. For more capacity use two or more separate banks if you have differently aged or rated or branded batteries. The extra Peukert losses are not a total dealbreaker except at extremely high discharge currents.
1976 electric Cal 2-27, MR WIGGLES
1979 Bruce Roberts Offshore 44, BRUTE FORCE
GrowleyMonster is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Deep-Cycle Flooded/wet lead-acid batteries used as STARTER batteries? (Trojan T-105) ErikFinn Electrical: Batteries, Generators & Solar 9 22-08-2014 17:33
Old Bank - New Bank belizesailor Electrical: Batteries, Generators & Solar 0 21-08-2012 12:07

Advertise Here

All times are GMT -7. The time now is 01:59.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.