understanding Gel deep cycle battery charging

[Islam Ghunym]

I got 3 x 100 amps 12 V group of batteries on parallel connected to a custom inverter which also charges the batteries and switch to another power source like UPS exactly.

I had some doubts about the inverter if it is actually charging the batteries properly so I connected a multi meter terminals to inverter terminals and measured less than 9 V!! on the lowest step then measured the higher steps (second was around 9V, third 9.7 V, 4th 10.2, 5th 10.7, 6th 11, last  11.25!) but these are all lower than the required voltages to recharge batteries.

 

batteries manufacturer gave info about proper charging current and voltages:

 

13.5-13.8 stand by

14.4-14.8 cycle use

25 A MAX x number of batteries so in my case 3 x 25 = 75 A MAX

 

now we all know that lower voltages is more healthy to battery life but it may not be enough to fully recharge the batteries, but 13.5 V on cycle use would be enough for me

 

what is actually happening is that batteries are getting charged to 14.4 V before the charger decides to stop at 14.4 V with these very low voltages (9-11V) it is charging, but how is this happening. (of course battery voltage will drop after 15 minutes to 12.8 or 12.9 which means batteries are fully charged)

 

what I can finally add is that inverter abilities is high 1500W and I can lower this by 7 steps so each step should minus the 1500W by 200W so on 9V it should outpot 200W and on full abilities (11.25 V) it should do 1500W.

 

it is a manual charger.

 

I usually put it on 6th step which will charge the batteries to 14.4 V with 25 to 15 amps at charging stop in around 2 hours at 20% cycle use (60 Amps)

 

with all these details my question is: how could this low voltages charge the batteries and is this a good thing or it will damage those deep cycle Gel batteries.

[Bombastinator]

3 minutes ago, Islam Ghunym said:

I got 3 x 100 amps 12 V group of batteries on parallel connected to a custom inverter which also charges the batteries and switch to another power source like UPS exactly.

I had some doubts about the inverter if it is actually charging the batteries properly so I connected a multi meter terminals to inverter terminals and measured less than 9 V!! on the lowest step then measured the higher steps (second was around 9V, third 9.7 V, 4th 10.2, 5th 10.7, 6th 11, last  11.25!) but these are all lower than the required voltages to recharge batteries.

 

batteries manufacturer gave info about proper charging current and voltages:

 

13.5-13.8 stand by

14.4-14.8 cycle use

25 A MAX x number of batteries so in my case 3 x 25 = 75 A MAX

 

now we all know that lower voltages is more healthy to battery life but it may not be enough to fully recharge the batteries, but 13.5 V on cycle use would be enough for me

 

what is actually happening is that batteries are getting charged to 14.4 V before the charger decides to stop at 14.4 V with these very low voltages (9-11V) it is charging, but how is this happening. (of course battery voltage will drop after 15 minutes to 12.8 or 12.9 which means batteries are fully charged)

 

what I can finally add is that inverter abilities is high 1500W and I can lower this by 7 steps so each step should minus the 1500W by 200W so on 9V it should outpot 200W and on full abilities (11.25 V) it should do 1500W.

 

it is a manual charger.

 

I usually put it on 6th step which will charge the batteries to 14.4 V with 25 to 15 amps at charging stop in around 2 hours at 20% cycle use (60 Amps)

 

with all these details my question is: how could this low voltages charge the batteries and is this a good thing or it will damage those deep cycle Gel batteries.

What chemistry is “gel”?

[Islam Ghunym]

3 hours ago, Bombastinator said:

What chemistry is “gel”?

lead acid in gel form

[Bombastinator]

7 minutes ago, Islam Ghunym said:

lead acid in gel form

Ok. Thanks.  I’d never heard the term.  I read a lot about lithium batteries and I know there are a bunch of different chemistries.  Iirc it’s not just that it is low power it actually has to be.

batteries aren't electrical so much as chemical.

 

a rechargeable battery is a reversible chemical reaction.  When you charge and drain a rechargeable battery you’re generally turning a bunch of metal into an oxide and back again.  It can only be done so fast and it produces heat.  That heat needs to drain away and it can only do it so fast.  There’s an iron reaction that can be used for batteries. The Chevy bolt uses em iirc.  They save old cannon from shipwrecks using the same thing.  They haul up a hunk of rust and turn it back into iron again by running a tiny charge of electricity through it for a couple months.  The slower you go the better it works.

[Islam Ghunym]

7 hours ago, Bombastinator said:

Ok. Thanks.  I’d never heard the term.  I read a lot about lithium batteries and I know there are a bunch of different chemistries.  Iirc it’s not just that it is low power it actually has to be.

batteries aren't electrical so much as chemical.

 

a rechargeable battery is a reversible chemical reaction.  When you charge and drain a rechargeable battery you’re generally turning a bunch of metal into an oxide and back again.  It can only be done so fast and it produces heat.  That heat needs to drain away and it can only do it so fast.  There’s an iron reaction that can be used for batteries. The Chevy bolt uses em iirc.  They save old cannon from shipwrecks using the same thing.  They haul up a hunk of rust and turn it back into iron again by running a tiny charge of electricity through it for a couple months.  The slower you go the better it works.

I am actually very surprised that you have never heard about deep cycle gel batteries. This type of batteries uaed mainly in solar system "no solar system without it".

Thx for info anyway.

[Bombastinator]

3 hours ago, Islam Ghunym said:

I am actually very surprised that you have never heard about deep cycle gel batteries. This type of batteries uaed mainly in solar system "no solar system without it".

Thx for info anyway.

I’ve heard of deep cycle lead acid.  It was the word gel that made me not know what chemistry you were talking about.