Fogstar drift 105ah DC-DC charging issues

[Stowaway]

I am hoping some kind sole could please point me in the right direction with my Fogstar drift charging issue. I have a 105ah Drift on my Chausson Flash 10 Transit. Charging through the CBE onboard system I get about 17amps as indicated on the Fogstar app, (not totally reliable I know). This charges the hab battery (but not on lithium spec I know). I wanted to boost this charge rate, so I have fitted a Renogy DC-DC dual input 50A (solar disconnected at moment).
Using 16mm wiring all seemed good except that when charging from both the CBE onboard system and the Renogy DC-DC, the 60A breaker from the DC-DC charger trips when the DC-DC output is set to 50A. Fogstar app indicated max charging reached is about 40A, then 'click', no more from DC-DC. I have changed breakers, replacing the 60A with a new one, and for a trial even tried replacing the 60A with an 80A in the DC-DC line. Both 60A and 80A continue to trip even though the Fogstar app still indicates 40A charge then 'click'. I have reduced output on the DC-DC charger to 30A and max charge indicated on the Fogstar battery app is about 35A but no breaker tripping. As the spec for the battery indicates 100A max charge, where am I going wrong? Any suggestions most welcome. Thanks.
G.

 

[fred_jb]

What kind of breaker are you using? My Renogy DC-DC came with a 60A fuse, but no circuit breaker.

 

[Stowaway]

Both 60a and 80a are the inline breaker type. I wanted to ability to disconnect various parts of my system, ie b2b from CBE input if required.

 

[fred_jb]

Both 60a and 80a are the inline breaker type. I wanted to ability to disconnect various parts of my system, ie b2b from CBE input if required.

It would be useful to know the make and model as I believe some of these automatic breakers are notoriously inaccurate in their ratings, though from what I have read they mostly trigger at much higher than rated loads so don't give much protection from overloads to the wiring. You also need to ensure that any breakers used are specifically rated for DC rather than AC use. You should probably have suitably rated inline fuses as well in any case. I would trust a good quality fuse much more than a breaker.

If you don't have a fuse already, you could fit one, say 40A or 50A, and if that does not blow but the breaker operates then you will know the breaker is the problem. Instead of combining the function of fuse and switch in one device it might be better to use fuses for protection and a manually operated isolation switch for connecting stuff - like the following. I use one of these for isolating my solar panels.

https://www.amazon.co.uk/Isolator-Disconnect-Photovoltaic-Miniature-Waterproof/dp/B0C6Y6593K?tag=mhf04-21

 

[Lenny HB]

Unless you used a quality DC breaker (they cost about £60) they will be a waste of time, the cheap ones are totally unreliable.

Reguarding the CBE charger have you check if it has an automatic equalization phase because if it has it is not suitable for charging Lithium.

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[fred_jb]

Another thought on this. When you say you get 17A charging through the onboard CBE system, is that through a split relay connection directly from the starter battery/alternator when the engine is running? If so I don't see how you can be charging from both the CBE and the Renogy B2B unit. Surely it is one or the other?

As I understand it a B2B normally takes a starter battery connection as input and outputs a boosted version of this voltage to connect to a power distribution unit in place of the original direct battery connection. So, the output of the B2B should take the place of the direct battery connection into the CBE split charge relay. At least that's how it works with my system. You absolutely do not want the boosted voltage coming out of the DC-DC connecting to the same input as a direct connection from the battery.

The other thing you could try is sending the output from the B2B directly to the leisure battery rather than through the CBE. I this case you would need to disconnect the starter battery from the input which normally goes to the split charge relay in the CBE. I have done this with my system and it works fine. The starter battery connection to the split relay input on the Electroblock must be left unconnected in this configuration.

 

[Lenny HB]

Have you disconnect
the split charge relay in the CBE distribution unit?

If you haven't it will short out the B2B, some units you can do it by snipping the zero ohm link R37 otherwise you may need to fit a bypass relay.