325ah Trojan bank max Inverter charger current

[hammick]

My Schneider Conext SW4048 Inverter bit the dust so they sent me an XW5548. I've gone from max Inverter charging of 45a to 110a. My battery bank is eight Trojan L16RE-A batteries for a 48v 325ah bank. What is the max current I can safely bulk charge these batteries (C/10 is only 32.5 amps)? I'd love to minimize diesel genset run time but not at the expense of battery life. Thanks.

[Sunking]

Great battery choice. Keep in mind C/10 is generic safe recommendation for all batteries. Yours are an exception and C/6 is no problem. 60 amps requires a 5 Kw generator, That will give you minimum gen run time and best efficiency,. Assuming you not run then down below 80% you recharge in 4/5 hours. 2 would be normal.

[hammick]

Great battery choice. Keep in mind C/10 is generic safe recommendation for all batteries. Yours are an exception and C/6 is no problem. 60 amps requires a 5 Kw generator, That will give you minimum gen run time and best efficiency,. Assuming you not run then down below 80% you recharge in 4/5 hours. 2 would be normal.

Thanks. Do you believe the often cited theory that you can charge at any current you like until the batteries reach 2.4 volts per cell at 77 degrees Fahrenheit?

My generator use is mostly during winter cloudy days and I don't run it unless I'm around to monitor voltage. Battery temp sensor is installed on battery lug. I usually charge to 90% and let the solar take over.

I use an MEP-802a military diesel genset which is 5kw. It's 80% rated so it's actually roughly a 6kw genset at my 5,200' elevation

Do you think I am safe bulk charging at max charging rate as long as I shut it down at 57.6 volts? Then let the solar take over?

[Mike90250]

I use an MEP-802a military diesel genset which is 5kw. It's 80% rated so it's actually roughly a 6kw genset at my 5,200' elevation....

First time I've seen elevation increase a genset power. Maybe you are not using standard terms?
Gensets are rated at 100% power for 60 min or 80% indefinitely. Be sure you are not tricking yourself or doing the calculation bassakwards.

Battery charging is very demanding load on a genset

When I run mine, I charge at max rate (30A on my 3Kw rated Lister) At the end of bulk, the rate starts to taper off, and I usually shut down at about 20A going to the batteries,

Be sure you run 2-5 min cooling at no load before you shut off the genset, or the heavy continuous load, can allow residual heat to build up in the alternator windings and melt things if you just shut it off.

[hammick]

First time I've seen elevation increase a genset power. Maybe you are not using standard terms?
Gensets are rated at 100% power for 60 min or 80% indefinitely. Be sure you are not tricking yourself or doing the calculation bassakwards.

Battery charging is very demanding load on a genset

When I run mine, I charge at max rate (30A on my 3Kw rated Lister) At the end of bulk, the rate starts to taper off, and I usually shut down at about 20A going to the batteries,

Be sure you run 2-5 min cooling at no load before you shut off the genset, or the heavy continuous load, can allow residual heat to build up in the alternator windings and melt things if you just shut it off.

Sorry for not being clearer. The military de-rates their gensets by 20%. So the 5kw MEP-802a can actually do 6kw easily. I've load tested them at 125% with no issues. At 5,200' mine probably won't do more than 110% but I don't need that much power anyhow. I have a 3kw model as a backup but it isn't trailer mounted and it's an inverter model (MEP-831a) and not near as reliable as my 5kw.

Thanks for the info on cool down. My 5kw genset has an Onan badged two cylinder diesel that is made by Lister Petter. I always do a good warm up and cool down before and after charging.

[Sunking]

Thanks. Do you believe the often cited theory that you can charge at any current you like until the batteries reach 2.4 volts per cell at 77 degrees Fahrenheit?

In theory yes sir, but in practice does not work that way. The faster you charge, the longer it takes to ABSORB. At generically at C/10 when you you hit 2.4 vpc or ABSORB you are roughly 80 to 90% SOC and spend the next 4 to 6 hours gassing (wasting water) and corroding the plates. Not real desirable. If you charge at say C/4 you hit ABSORD (2.4 Volts) more than twice as fast, but when you hit ABSORB are only 60% SOC which means you will be in ABSORD mode twice as long. You do not gain anything in time, you only loose by loosing more water and more corrosion which will significantly shorten battery life.

So here is your homework assignment to answer your question. Look in your Trojans Owner Manual and look for the RECOMMENDED CHARGE RATE. I twill be the rate that gives you the best of both worlds. High enough to prevent Stratification, minimize charge time, minimum damage, and longest battery cycle life. It should be if memory serves me correctly 13% of the battery C/6 AH capacity. That way you will know for sure and never forget it.

[hammick]

In theory yes sir, but in practice does not work that way. The faster you charge, the longer it takes to ABSORB. At generically at C/10 when you you hit 2.4 vpc or ABSORB you are roughly 80 to 90% SOC and spend the next 4 to 6 hours gassing (wasting water) and corroding the plates. Not real desirable. If you charge at say C/4 you hit ABSORD (2.4 Volts) more than twice as fast, but when you hit ABSORB are only 60% SOC which means you will be in ABSORD mode twice as long. You do not gain anything in time, you only loose by loosing more water and more corrosion which will significantly shorten battery life.

So here is your homework assignment to answer your question. Look in your Trojans Owner Manual and look for the RECOMMENDED CHARGE RATE. I twill be the rate that gives you the best of both worlds. High enough to prevent Stratification, minimize charge time, minimum damage, and longest battery cycle life. It should be if memory serves me correctly 13% of the battery C/6 AH capacity. That way you will know for sure and never forget it.

Thanks. Trojan recommends 10 - 13% of C20. C20 for my batteries is 325ah so I will limit charging current to 42 amps (or I'm guessing the inverter will limit amps automatically based on my AH setting). I guess stepping up to the XW inverter with the 110 amp charger won't speed up genset charging for me. It will be nice down the road when I step up to a larger bank though.

The RV solar geeks are bulk charging their batteries at crazy high amps. Like 60, 80 or even 100 amps into a 208 ah 12v bank. Sounds like they are killing their batteries.

[Mike90250]

........The RV solar geeks are bulk charging their batteries at crazy high amps. Like 60, 80 or even 100 amps into a 208 ah 12v bank. Sounds like they are killing their batteries.

Wow Where do they manage to fit all the solar ?

[hammick]

Wow Where do they manage to fit all the solar ?

They are doing it with generators and converter chargers for when camping in the shade or it's not sunny.

[Sunking]

The RV solar geeks are bulk charging their batteries at crazy high amps. Like 60, 80 or even 100 amps into a 208 ah 12v bank. Sounds like they are killing their batteries.

Sorry I missed this earlier.

Not sure I would call them GEEKS or NERDS as that implies they know what they are talking about. Just plain foolish wannabe jibber jabber. Like i said you hit a WALL in charge rates where faster charge rates buy you nothing in terms of Time. It is also very dangerous as the Battery Plates, Grids, and Term Post are not likely designed to handle that high of a Charge/Discharge rate leading to catastrophic damage and/or fire. Just Like a loose connection under normal heavy load can do this. Note if this happens is your fault and no waranty claim or Law Suit can be filled. You would be SOL. Ignore those wannabe's.

[inetdog]

.... It should be if memory serves me correctly 13% of the battery C/6 AH capacity. ....

Just a question of notation, Dereck:

When you say 13% of C/6 do you really mean 13% of C₆ , the amp hour capacity at the 6 hour rate?
Otherwise some people will interpret what you wrote as 13% of 1/6 of C₂₀.

[Sunking]

Just a question of notation, Dereck:

When you say 13% of C/6 do you really mean 13% of C₆ , the amp hour capacity at the 6 hour rate?
Otherwise some people will interpret what you wrote as 13% of 1/6 of C₂₀.

Thanks Dave, I screwed that completely up and thank you for bringing that to my attention. My bad and I apologise. Generically and simple rule of thumb charge at C/7.7 of the battery the battery 20 hour capacity rate for best efficiency and time. If you charge faster does not shorten time overheats the battery, and can damage the battery. So if the battery is rated at 100 AH, ideal charge current is 100 AH / 7.7 hours = 13 amps. Check your batteries owners manual. You should see a Window of roughly C/12 to C/8 for FLA batteries. Or just go read the Stickies.

Thx again.

[hammick]

Great. I will make sure my genset charging doesn't exceed 45 amps. My solar charging tops out at 27 - 28 amps but I'll probably add three more panels to get it over 40a