Charging start battery from MPPT

[MtB]

48 minutes ago, Jak said:

Well that told me then!  The Halfords panels are tiny things. Just designed to keep a car battery topped up if you don’t use it much. No controller needed. I’ve had it a few years and it’s doing a good job so far. 

 

Well it strikes me as a good workable solution too. Simpler is nearly always better in my opinion. 

 

The complicated methods being suggested might make it more idiot-proof but this is only necessary if you plan to let idiots have charge of the boat. 

 

 

[Tony Brooks]

3 minutes ago, MtB said:

 

Well it strikes me as a good workable solution too. Simpler is nearly always better in my opinion. 

 

The complicated methods being suggested might make it more idiot-proof but this is only necessary if you plan to let idiots have charge of the boat. 

 

 

 

Jak's solution is idiot-proof, it is Rodtheplod's that is not. I got them mixed up.

[ditchcrawler]

8 hours ago, rusty69 said:

I have used a similar method in the past. Such a small panel it didn't even have a solar regulator. One-two-both switch, which is open to human error, but it becomes habit to switch it when turning the engine off. 

 

Sometimes the simplest method is the best 

I have a can on my exhaust to stop the rain and snow coming down into the silencer/ exhaust valves, How many cans do you think I have lost starting the engine with it still on there

[rusty69]

2 minutes ago, ditchcrawler said:

I have a can on my exhaust to stop the rain and snow coming down into the silencer/ exhaust valves, How many cans do you think I have lost starting the engine with it still on there

Sounds like a piece of string might solve your problem. 

[ditchcrawler]

4 minutes ago, rusty69 said:

Sounds like a piece of string might solve your problem. 

  But now you are automating the system with the string to stop anything untoward happening when the ijet with the key turns it without remembering to do what he should have done first.  Safety systems are better than human memory 

[rusty69]

4 minutes ago, ditchcrawler said:

  But now you are automating the system with the string to stop anything untoward happening when the ijet with the key turns it without remembering to do what he should have done first.  Safety systems are better than human memory 

Well, yes. I suppose there is that. There is a possibility the string might snap,or the VSR fail like my memory. 

[GUMPY]

9 hours ago, Tony Brooks said:

I have a feeling that a panel of 10% or less of bank capacity does not need a controller, but please check those numbers.

Depends on the panel voltage.

If less than 20v you might get away with it. If more you won't.

1 hour ago, ditchcrawler said:

I have a can on my exhaust to stop the rain and snow coming down into the silencer/ exhaust valves, How many cans do you think I have lost starting the engine with it still on there

Don't you have it attached by a piece of string so you don't lose it.

The old calor gas cylinder tops were good for exhausts😉

 

[ditchcrawler]

15 minutes ago, GUMPY said:

 

Don't you have it attached by a piece of string so you don't lose it.

The old calor gas cylinder tops were good for exhausts😉

 

As I don't have any more cans and I have painted this one in the boat colours I now remember. I wonder how many flat starter batteries are needed before you remember. It gas ones look just the job, of course I could go totally automatic and fit a flapper 

[GUMPY]

7 minutes ago, ditchcrawler said:

As I don't have any more cans and I have painted this one in the boat colours I now remember. I wonder how many flat starter batteries are needed before you remember. It gas ones look just the job, of course I could go totally automatic and fit a flapper 

Something in the back of my brain tells me the exhaust pipes had the same thread on top as the calor caps. If forgotten fhat would have made trying to start the engine  interesting.

[MtB]

2 hours ago, ditchcrawler said:

I have a can on my exhaust to stop the rain and snow coming down into the silencer/ exhaust valves, How many cans do you think I have lost starting the engine with it still on there

 

I have a 2 1/2" BSP screwed cap on my exhaust. How many times do you think I've found the engine won't start and I've thought "OMG what on EARTH is wrong, this seems serious"?! 

[GUMPY]

1 hour ago, MtB said:

 

I have a 2 1/2" BSP screwed cap on my exhaust. How many times do you think I've found the engine won't start and I've thought "OMG what on EARTH is wrong, this seems serious"?! 

Not once 😱😂

[MtB]

2 hours ago, GUMPY said:

Not once 😱😂

 

CORRECT!!!!

 

[blackrose]

Does anyone have a VSR recommendation? I'm thinking 125 amp single sensing?

 

I already have a 125A VSR between my start and BT batteries which splits the charge from my start alternator and also from one of my mains battery chargers.  If I fit an additional VSR between domestics and start batteries that will then activate the first VSR so any charge going to my start battery would then be split to BT batteries. Is there any need for more than 125 amp VSR? My MPPT is 60 amp, combined chargers are 70amp and alternators are 70 amp each.

 

Any brands to buy or avoid? There are lots of cheap ones on eBay. Would they be any good or should I be going for a known brand?

 

 

Edited June 1, 2023 by blackrose

[Tony Brooks]

Cargo seem a fairly reputable brand in the autoelectrical after-market. SirN seemed to use the brand. The one I bought was 140 amp. The trouble is one does not know if the brand is only label deep.

 

 

[blackrose]

Ok thanks Tony. A friend recommended Blue Sea but they're very expensive.

[David Mack]

Mine is a BEP dual sensing VSR and rated at 140A. It has worked fine. The current equivalent model is labelled as 'digital' with electronic operation, but I don't know how different it really is to my older version.

 

[blackrose]

I have a BEP 125A VSR between my start and BT batteries. It's also an old model. 

 

They seem to range in price from £20 on eBay to over £100 for Blue Sea. The BEP one you mention is about £70. I wonder what the difference is?

 

This one is supposed to be the best on the market.

 

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

 

Don't all VSRs isolate the start battery during engine cranking?

Edited June 1, 2023 by blackrose

[Tony Brooks]

7 hours ago, blackrose said:

I have a BEP 125A VSR between my start and BT batteries. It's also an old model. 

 

They seem to range in price from £20 on eBay to over £100 for Blue Sea. The BEP one you mention is about £70. I wonder what the difference is?

 

This one is supposed to be the best on the market.

 

https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

 

Don't all VSRs isolate the start battery during engine cranking?

 

Normally yes, because the battery voltage is below the turn on threshold, but if you have well charged batteries and enough charging bring provided at the time then tit may not. However, as the batteries will have to be well charged, it won't really matter if it did not. If that is what you want, then you need an ordinary split charge relay controlled by the alternator output or a zero volt drop split charge diode.

[blackrose]

I've just bought this BEP unit. Found one on eBay for 50 quid.

 

https://www.bepmarine.com/en/p/710-140A/Digital-Voltage-Sensing-Relay-DVSR

[CIEL]

On 28/05/2023 at 10:29, Jak said:

Well that told me then!  The Halfords panels are tiny things. Just designed to keep a car battery topped up if you don’t use it much. No controller needed. I’ve had it a few years and it’s doing a good job so far. 

That's exactly my set up.  It's been that way on both of the boats I've had since 2001.  A word of caution is to make sure you allow enough cable for when you open the hatch! DAMHIK.

Chris