Battery-to-Battery 12v-to-12v battery charger - Aliexpress

[flynmoose]

Anyone have any experience with one of these?

9.82US $ 15% OFF|12v/30a Dc To Dc Charger With Bluetooth Automatic Smart Battery Chargers For Rvs, Campers, Ships Bs123020 Charger - Network Analyzers - AliExpress

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Sterling is way too expensive.
Renogy is better.

But I just wrestle with paying $230-250 for a device that really only exists to keep my soon-to-be lithium battery bank from sucking current too fast from the alternator.

Then again - I had a taste of why I need one. Had the inverter on - kids ran the microwave to re-heat something. We were parked briefly and the engine was idle. Things got a little warm! Out of curiosity I briefly duplicated the situation and had my DC clamp meter on the cable coming from the alternator to the battery bank. 145A. Batteries are fully charged and capable of running the microwave for 2 minutes - but because the voltage output of the alternator is higher, all the current comes from the alternator instead of the battery.

So putting a "valve" in the middle is way cheaper than a new MB alternator.

Renogy 60A (DCC1212-60) can be had for $240 right now.
Renogy 40A is $180
This AliExpress box is only 30A but it is more than half the price. ($110 with the BT module.)
Renogy 20A is $120.

Thoughts? Anyone bought one yet and comment on the junk factor?

 

[Short_Shot]

Personally I refuse to trust my equipment and possibly life to cheap stuff and would not recommend anyone else use something like that.

I'd get the renogy, but keep in mind that 20a is very little power for a system with higher power devices and would be a lot of idling - but 30a still needs a lot of idling too.

That said. Regarding junk factor, it might be a really good deal and a solid product. Many Chinese products are just clones of stuff we get in our market anyways, and sometimes are the exact same unit.

For the price and source I'd wager it has poor controls, and will burst into flames at a light sneeze. It may be rated for 30a but might be designed with zero safety factor in mind. I've been wrong before though.

And that it's worth buying and testing and reporting results if one was so inclined to risk the money and time.

 

[flynmoose]

Thanks. Obviously I had concerns so I was asking about anyone who actually bought one @Short_Shot.

I don't idle. 30A continous for many hours of driving would go a long way to keep my battery topped off. No illusion I am going to quickly recharge a depleted battery. And should have mentioned that I will be putting 4-600watts of solar on the RV roof.

Back to my real reason I am looking at this solution - clearly I could smoke the alternator with too much draw (either now with an inadvertent large power drain from the inverter with flooded batteries - or in the future with depleted batteries that are hungry to eat anything the alternator will let it have. I don't want to routinely be pulling 150+amps off the alternator.

 

[israndy]

Good find! They also seem to offer a 60 amp version for $165 with free shipping:

163.19US $ 41% OFF|12v 60a Charger Booster For Rvs, Campers, Ships Dc To Dc Charger Support Bluetooth Automatic Smart Battery Chargers - Solar System Accessories - AliExpress

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And a version with solar inputs up to 50v for $227

The Renogy 60 amp DC-DC is $259 (on sale for $233 right now) and you cannot get a bluetooth app or display for it.

The 50 amp DC-DC+Solar is $299 ($263 on sale)

My current setup has a separate solar charger, I like that both solar and alternator are charging the battery, although their charge algorithms probably get screwed by going at the same time.

I believe the Renogy unit will use solar power, if available, instead of alternator power. Wonder what the Chinese one would do.

 

[flynmoose]

Had not seen the AliExpress All-in-one charger/controller.

I did look at the Renogy and ruled it out based on these review comments:

- solar input is only 25v VOC so basically you can only use one standard panel, or multiple panels wired in parallel. This is ok for me since alternator charging is the primary power source, with solar backup.
- a more serious issue is when solar is active, max amps are limited to 25 amps each for alternator and solar. This might be the source of some of the complaints.

The problem with that second statement is that you might only get 30 amps of charge if the solar is producing a small amount of power (say 5 amps) and it truly throttles alternator to 25A if ANY power is coming from solar. Or it may just mean that it is 50a limited in some combination of solar and alternator - which would be fine if that is what you want.

The AliExpress version 50V and 30A for solar - but the downside is that the box ignores solar while alternator power is coming in. To your point - not sure what happens when you have a separate MPPT and the DC-DC both trying to charge. In theory if their charge profiles are matched identically (Bulk,Abs,Float) then you are just providing more amps at the same voltage - but I imagine you can't get them perfect even if the profile is programmable which means that one box will switch from Bulk to Abs before the other. Newbie so I don't know enough about voltage sensing and profiles to know what happens.

I'm leaning towards a dedicated MPPT (EPever) so I can run my panels in series with higher voltage and then either the Renogy 60A or taking a gamble on the AliExpress 60A. $80 savings but a big gamble without any usage history from someone here. As @Short_Shot pointed out - the whole thing could go up in smoke as soon as it gets a few amps through it.

 

[Download7]

Did you end up ordering one from Ali?

 

[israndy]

I found the 60 amp Renogy one on eBay used for $99, hope it works, it shipped almost immediately so that's a good sign