DC-DC charger with "charge limiting" port

2126 Views 18 Replies 7 Participants Last post by SteveSS, 10 mo ago

dlotto

Discussion Starter · May 25, 2022

I am installing a Renogy 60A DC-DC charger in my system. There is not good information in the manual on the purpose of the "charge limiting" connection which apparently reduces the maximum capacity by 50%. In surveying some of the DIY youtube contributions, I gather that a lithium battery's capacity can overwhelm the vehicle alternator, especially at low rpms.

I am considering installing the charge limiting connection with a toggle on the dashboard so that the default is 50% of the charger capacity, i.e. 30A. When driving at highway speed, if I need to do a lot of charging I could toggle the charge limiting connection to allow the full 60A.

Anyone have any experience with this charger? Any insights on how to handle the charge limiting connection.

1 - 19 of 19 Posts

SteveSS

· #2 · May 25, 2022

Which alternator do you have? According to Renogy guidelines, 50A is the largest DC-DC recommended for the stock 180A alternator. The 60A is only appropriate if you have the optional 220A alternator. See this recent thread for more info on alternator loading. I have a Renogy DC-DC and I installed switches on both the D+ and LC wires. It never hurts to maximize your control options.

Reactions: 2

proeddie

· #3 · May 25, 2022

SSS,

Is your DC-DC unit the 40A version?

dlotto

Discussion Starter · #4 · May 25, 2022

60A, probably oversized it.

phil

· #5 · May 25, 2022

dlotto said:
60A, probably oversized it.

you could pull 60 amps as long as you know what the other accessories are pulling

just driving with nothing on is approximately 20-24 amp, plenty of room for a 60 amp charge

SteveSS

· #6 · May 25, 2022

proeddie said:
SSS, Is your DC-DC unit the 40A version?

Mine is 60A, but I have the 220A alternator.

SteveSS

· #7 · May 25, 2022

phil said:
you could pull 60 amps as long as you know what the other accessories are pulling
just driving with nothing on is approximately 20-24 amp, plenty of room for a 60 amp charge

Which is the reason I installed switches on my Renogy's D+ (on-off) and LC (1/2 power) control wires. Those give me max control over the DC-DC and its draw on the alternator.

BTW, the Renogy manual says: "When the battery charger is sending the rated amps, the input side
may experience a higher current draw by a factor of up to 50%." I asked Renogy under what conditions that would happen and didn't get a straight answer. The few times I have checked alternator output with a clamp meter, I haven't seen that happening. But it's one more thing to consider if using a 60A DC-DC with a 180A alternator.

Reactions: 1

e.haase01

· #8 · 10 mo ago

I have the 220A alternator on a 2021 136. I am using zero gauge wire all the way up to the starter battery. I can only get it to work on 30A - when I use the full 60A I pops my 100A breaker. I am trying to charge two 200AH Renogy AGM batteries that are running a Dometic DC AC unit. Any help would be appreciated.

Renogy said I had a defective unit but the replacement unit is doing same thing.

Any help would be appreciated!

GaryBIS

· #9 · 10 mo ago

e.haase01 said:
I have the 220A alternator on a 2021 136. I am using zero gauge wire all the way up to the starter battery. I can only get it to work on 30A - when I use the full 60A I pops my 100A breaker. I am trying to charge two 200AH Renogy AGM batteries that are running a Dometic DC AC unit. Any help would be appreciated.

Renogy said I had a defective unit but the replacement unit is doing same thing.

Any help would be appreciated!

Hi,
A clamp meter would let you see what the actual amperage is, and see if the DC to DC charger is putting out too much current.
It has to be a clamp meter that will read DC current - some of them only do AC.

Gary

proeddie

· #10 · 10 mo ago

So to answer the original question, if you connect the D+ AND LC connections on the B2B to 12V, it will drop to 30A charging... disconnect LC and it will charge at 60A

SteveSS

· #11 · 10 mo ago

e.haase01 said:
I have the 220A alternator on a 2021 136. I am using zero gauge wire all the way up to the starter battery. I can only get it to work on 30A - when I use the full 60A I pops my 100A breaker. I am trying to charge two 200AH Renogy AGM batteries that are running a Dometic DC AC unit. Any help would be appreciated.

Renogy said I had a defective unit but the replacement unit is doing same thing.

Any help would be appreciated!

Could also be a bad breaker, especially if it's a cheap knockoff. Maybe try a 100A fuse instead.

Reactions: 1

e.haase01

· #12 · 10 mo ago

Thanks for the feedback ( this forum is amazing). I ordered a new breaker, the same brand ( T-Spec ) and it will be here on Friday.

Thanks SteveSS - I read through your posts and it seems you are running same DCDC Charger I'm trying to get to work. I was doing chassis ground but tried running 0 gauge to the starter battery and that did not help. I may try see if I can find a 100A ANL fuse to try - calling around cant find anyone that has one in the DFW area.

Under time crunch my set up will only run the AC for one night and need as much charge as possible to get through second night - suppose to be camping this weekend and my wife has zero patience for these things

HarryN

· #13 · 10 mo ago

e.haase01 said:
I have the 220A alternator on a 2021 136. I am using zero gauge wire all the way up to the starter battery. I can only get it to work on 30A - when I use the full 60A I pops my 100A breaker. I am trying to charge two 200AH Renogy AGM batteries that are running a Dometic DC AC unit. Any help would be appreciated.

Renogy said I had a defective unit but the replacement unit is doing same thing.

Any help would be appreciated!

Breaker:

Which exact breaker are you trying to use?
If it is tripping at 60 amps, then it might simply be the wrong breaker.
Unfortunately there are a lot of low quality breakers on the market
It might also be that the total load going through the breaker (loads plus charging) are exceeding the rating

Try one of these:

Series 187 Surface Mount Thermal Switchable Circuit Breaker - Blue Sea Systems | Fisheries Supply

Save More on Your Blue Sea Systems Series 187 Surface Mount Thermal Circuit Breaker at Fisheries Supply. Excellent Customer Service, Ready to Ship. Marine Supplies Since 1928!

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As a practical matter, it is going to be very challenging to run an air conditioner off of 2 x renogy AGM batteries. They have completely the wrong discharge curve for that application.

It is difficult with ANY AGM battery, but just consider to either switch to 4 each high quality AGMs or LiFe.

What you have now is a minimalist electrical system (with sufficient capacity to keep up with refrigeration) trying to run a heavy duty load setup.

I am just guessing that your run time with the a/c will be perhaps an hour?

Buy a 3 kW inverter generator.

See less See more

e.haase01

· #14 · 10 mo ago

HarryN said:
Breaker:

Which exact breaker are you trying to use?

If it is tripping at 60 amps, then it might simply be the wrong breaker.

Unfortunately there are a lot of low quality breakers on the market

It might also be that the total load going through the breaker (loads plus charging) are exceeding the rating

Try one of these:

See less See more

GaryBIS

· #15 · 10 mo ago

Hi,
If you have the RTX 2000 DC air conditioner, this video gives some idea of the performance and hours of operation you might expect under moderately hot conditions..

It appears to be an efficient AC of moderate size (6800 BTU/hr), and since it runs on DC there are no inverter electrical losses or inverter heat gains. Draws 35 amps on full power and 19 amps on ECO.

I really think getting a clamp meter would help you figure out the source of the trouble - certainly sounds like something is broken. I'd suspect a cheap breaker - I've had two cheap Amazon breakers fail in a mode where they open way below their rated amperage.

Gary

e.haase01

· #16 · 10 mo ago

GaryBIS said:
Hi,
If you have the RTX 2000 DC air conditioner, this video gives some idea of the performance and hours of operation you might expect under moderately hot conditions..

It appears to be an efficient AC of moderate size (6800 BTU/hr), and since it runs on DC there are no inverter electrical losses or inverter heat gains. Draws 35 amps on full power and 19 amps on ECO.

I really think getting a clamp meter would help you figure out the source of the trouble - certainly sounds like something is broken. I'd suspect a cheap breaker - I've had two cheap Amazon breakers fail in a mode where they open way below their rated amperage.

Gary

Thanks Gary!

I didn't own a clamp meter or ever used one before today. Based on your suggestion I had Amazon drop one off about an hour ago.

I first tested the LC in which has been working fine. That was gave me 31.5 amps. When I disconnected the LC and retested I got 71 amps for a little less than 2 mins before the 100 amp breaker popped. I have another breaker coming on Friday - hopefully that solves the issue.

Thanks for your help!

e.haase01

· #17 · 10 mo ago

Thank you everyone for the help. The new breaker fixed the problem.

It was was interesting the 60 amp DC/ DC charger quickly got to 70amps of draw in the first two mins, then went to 75 for about 5 seconds then got down to 59.5 over the next minutes.

I think I am going to follow Steve's setup and put the LC on a switch.

Reactions: 1

proeddie

· #18 · 10 mo ago

If you get a DPDT center-off switch, you can use it's 3 positions:

center = charging off
left = charging at 60A
right charging at 30A

You only need 3 wires going to the switch... 12+ , D+ wire, LC wire

Reactions: 1

SteveSS

· #19 · 10 mo ago

e.haase01 said:
Thank you everyone for the help. The new breaker fixed the problem.

It was was interesting the 60 amp DC/ DC charger quickly got to 70amps of draw in the first two mins, then went to 75 for about 5 seconds then got down to 59.5 over the next minutes.

I think I am going to follow Steve's setup and put the LC on a switch.

Glad to hear it was just the breaker. FWIW, the Renogy manual says the unit can sometimes draw up to 1.5X its rated output current. That's 90A max for their 60A DC-DC. You briefly saw 75A. Because of that 90A max, I cabled and fused the input on mine for 100A just to be safe.

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