Bow Thruster - Would another battery in parallel make much difference to the amount of thrust?

Elessar said:
Agreed. 800CCA sounds fine. No idea what 50A means in this context.
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It means the battery has 50 Amp Hour capacity. In theory, you can draw the 800 amps for 3.75 minutes before the battery was empty. In reality, lead acid cells don't work like that, so usable capacity much less.

I linked to the battery spec in my post above #3

https://www.exidegroup.com/eu/en/battery/EM1000

In the OPs case, his bow thruster will draw up to 500 amps (well within the CCA capability of the battery). The problem is the capacity is low so it drains pretty fast (see tables elsewhere for terminal voltage as a relationship of battery state of charge for a 12v lead acid battery).

His battery is too small for this purpose.
 
Quick and dirty calcs.
5kw motor at 12v can draw 400A. At 11v (assume worse case) the draw is about 450A. You are limited to 3 minutes run time so 3 mins is 0.05hrs.450A draw for 0.05 hours is circa 23Ah out of the battery. So a battery with over 500cca and 50Ah capacity would be the absolute minimum. A good 100Ah AGM with circa 800A CCA or something like that would provide a healthy margin. Hope that helps
 
wonkywinch said:
It means the battery has 50 Amp Hour capacity. In theory, you can draw the 800 amps for 3.75 minutes before the battery was empty. In reality, lead acid cells don't work like that, so usable capacity much less.

I linked to the battery spec in my post above #3

https://www.exidegroup.com/eu/en/battery/EM1000

In the OPs case, his bow thruster will draw up to 500 amps (well within the CCA capability of the battery). The problem is the capacity is low so it drains pretty fast (see tables elsewhere for terminal voltage as a relationship of battery state of charge for a 12v lead acid battery).

His battery is too small for this purpose.
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Why would it say 50A if it means 50 Ah.
They are completely different measures

One is the rate of flow of electricity. One is the amount of electricity that is stored. They are not related.
 
Elessar said:
Why would it say 50A if it means 50 Ah.
They are completely different measures

One is the rate of flow of electricity. One is the amount of electricity that is stored. They are not related.
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Because there is an error in the manual as I explained. Have you clicked on the battery spec sheet for the battery the OP says he has or do you just enjoy being confrontational without reading the thread content first?
 
I think the 300Amp quote in the manual is an error, it should read 300Ah. But, that's nonsense, a 5Kw thruster does not need that many Ah. I agree with Geem in post #22, 100Ah, 800CCA battery would be ideal.

The initial terminal voltage of 10.6V is to be expected, the thruster motor will be rated for this, not 12V. 10.2V after 45 seconds is a little low, possibly due to the low Ah of the battery, or more likely the battery is a little tired.
 
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PaulRainbow said:
I think the 300Amp quote in the manual is an error, it should read 300Ah. But, that's nonsense, a 5Kw thruster does not need that many Ah. I agree with Geem in post #22, 100Ah, 800CCA battery would be ideal.

The initial terminal voltage of 10.6V is to be expected, the thruster motor will be rated for this, not 12V. 10.2V after 45 seconds is a little low, possibly due to the low Ah of the battery, or more likely the battery is a little tired.
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Many thanks for the various comments - it looks as if the battery has enough CCA to nudge the bow, but only for about 45 secs (which is ok-ish). And doubling the battery wont give much more thrust, but will increase the time. It is in fact a new battery, having replaced an Optima red top.

Given the voltage drop etc, might a 100Ah deep cycle leisure battery be better eg. Numax XV31MF?
 
therowans said:
Many thanks for the various comments - it looks as if the battery has enough CCA to nudge the bow, but only for about 45 secs (which is ok-ish). And doubling the battery wont give much more thrust, but will increase the time. It is in fact a new battery, having replaced an Optima red top.

Given the voltage drop etc, might a 100Ah deep cycle leisure battery be better eg. Numax XV31MF?
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The voltage drop to 10.6V is not an issue, the motor is rated for that. You can add as many Ah as you like, you can't change that. It is worth adding some Ah so the voltage doesn't drop even more, so quickly.

That Numax battery is not deep cycle, it's just a leisure battery, but it's an OK battery. This might be a slightly better choice, 925 CCA instead of 740CCA https://www.bmstechnologies.co.uk/product/yuasa-ybx3642-super-heavy-duty-commercial-battery/
 
The "manual" spec shown in post #3 was written by someone suffering from electrical dyslexia. For some models of thruster it specifies Minimum x Ah and for others it specifies Minimum y Amp - I suspect they mean Ah in both cases. There is a similar problem in another post here where capacity is cited in A/h, some curious derivative of current which has little meaning in this context.

As others have said, the key issue here is probably CCA which the "Manual" is silent about.

I have checked 3 suppliers of the Exide 1000 AGM battery and they all give 50 Ah and 800 CCA for this model. However, if the OP has a 50Ah battery where the "Manual specifies "Min 300 Amp" by which I think they mean "Min. 300 Ah" he may already have invalidated his warranty. It's a mystery to me why a model of BT which requires 300 Ah of battery capacity at 12V. also requires 300 Ah of capacity at 24 V. another sign that the manual was written by someone who doesn't understand electricity.

Measuring what's happening at the battery is of little help in these circumstances, try again while measuring at the motor terminals. If the battery Voltage has dropped to 10.2V there will certainly be a lower voltage at the motor. You say the cables looks "good and thick" just what cross section of cable is it? You need to find the rest of the manual, which apparently specifies cable sizes required and check that yours meets the numbers specified. You also need to get Volvo to clear up their confusion between A and Ah. Once it's clear what they require, replace your battery and cables to meet their minimum spec. Adding another 50Ah battery to one that is 1/6 the capacity specified is not helpful, better to put 2 x 150 Ah and consign the 50 Ah to another job. Make sure the cable terminals are well crimped on and properly bolted to both the motor and the battery.

Peter.
 
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PeterWright said:
The "manual" spec shown in post #3 was written by someone suffering from electrical dyslexia. For some models of thruster it specifies Minimum x Ah and for others it specifies Minimum y Amp - I suspect they mean Ah in both cases. There is a similar problem in another post here where capacity is cited in A/h, some curious derivative of current which has little meaning in this context.

As others have said, the key issue here is probably CCA which the "Manual" is silent about.

I have checked 3 suppliers of the Exide 1000 AGM battery and they all give 50 Ah and 800 CCA for this model. However, if the OP has a 50Ah battery where the "Manual specifies "Min 300 Amp" by which I think they mean "Min. 300 Ah" he may already have invalidated his warranty. It's a mystery to me why a model of BT which requires 300 Ah of battery capacity at 12V. also requires 300 Ah of capacity at 24 V. another sign that the manual was written by someone who doesn't understand electricity.

Measuring what's happening at the battery is of little help in these circumstances, try again while measuring at the motor terminals. If the battery Voltage has dropped to 10.2V there will certainly be a lower voltage at the motor. You say the cables looks "good and thick" just what cross section of cable is it? You need to find the rest of the manual, which apparently specifies cable sizes required and check that yours meets the numbers specified. You also need to get Volvo to clear up their confusion between A and Ah. Once it's clear what they require, replace your battery and cables to meet their minimum spec. Adding another 50Ah battery to one that is 1/6 the capacity specified is not helpful, better to put 2 x 150 Ah and consign the 50 Ah to another job. Make sure the cable terminals are well crimped on and properly bolted to both the motor and the battery.

Peter.
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Thank you, exactly what I was trying to say.
 
PeterWright said:
The "manual" spec shown in post #3 was written by someone suffering from electrical dyslexia. For some models of thruster it specifies Minimum x Ah and for others it specifies Minimum y Amp - I suspect they mean Ah in both cases. There is a similar problem in another post here where capacity is cited in A/h, some curious derivative of current which has little meaning in this context.

As others have said, the key issue here is probably CCA which the "Manual" is silent about.

I have checked 3 suppliers of the Exide 1000 AGM battery and they all give 50 Ah and 800 CCA for this model. However, if the OP has a 50Ah battery where the "Manual specifies "Min 300 Amp" by which I think they mean "Min. 300 Ah" he may already have invalidated his warranty. It's a mystery to me why a model of BT which requires 300 Ah of battery capacity at 12V. also requires 300 Ah of capacity at 24 V. another sign that the manual was written by someone who doesn't understand electricity.

Measuring what's happening at the battery is of little help in these circumstances, try again while measuring at the motor terminals. If the battery Voltage has dropped to 10.2V there will certainly be a lower voltage at the motor. You say the cables looks "good and thick" just what cross section of cable is it? You need to find the rest of the manual, which apparently specifies cable sizes required and check that yours meets the numbers specified. You also need to get Volvo to clear up their confusion between A and Ah. Once it's clear what they require, replace your battery and cables to meet their minimum spec. Adding another 50Ah battery to one that is 1/6 the capacity specified is not helpful, better to put 2 x 150 Ah and consign the 50 Ah to another job. Make sure the cable terminals are well crimped on and properly bolted to both the motor and the battery.

Peter.
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I agree with most of that Peter, but, it says 2x150 for the 24V variant, which is 150Ah at 24V

I don't agree with it needing 300Ah of capacity. If the motor draws a constant 400A it would take 20 mins to discharge the battery to about 50%, but the duty cycle is only 3 mins max.
 
The unit is old / obsolete and the long way forward is probably a new sidepower one - so it's really a case of keeping it going till it gives up. In practice I probably don't use more than 30-45 seconds between charges, so a modest increase in Ah seems like the best way forward for the time being. And in any case an extra 200 Ah in the bow would require an awful lot of beer at the back end to keep the boat in trim.....
 
Before messing around with batteries, check the voltage at the battery and at the thruster when the thruster is operating.

You might be surprised at how big the difference is which would indicate that you need either bigger cables or better connectors which are not rusted up or both.

I had a weak windlass - until I had new cables made up!

For batteries the key is CCA - cold cranking amps.
House batteries are not so good as starter batteries which are of course made for cranking engines and optimized for that.
 
westernman said:
Before messing around with batteries, check the voltage at the battery and at the thruster when the thruster is operating.
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Nothing wrong with the voltage at the battery.
westernman said:
You might be surprised at how big the difference is which would indicate that you need either bigger cables or better connectors which are not rusted up or both.

I had a weak windlass - until I had new cables made up!

For batteries the key is CCA - cold cranking amps.
House batteries are not so good as starter batteries which are of course made for cranking engines and optimized for that.
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Depends what is being used for the house bank, but either way, he has a dedicated thruster battery, it just isn't quite big enough.
 
westernman said:
And the voltage at the thruster??
If that is much lower than the battery voltage, the problem is the cables.
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10.6V with the thruster running is the correct voltage. If there were cabling issues the thruster would not work and/or the battery voltage cannot be pulled down to 10.6V
 
PaulRainbow said:
10.6V with the thruster running is the correct voltage. If there were cabling issues the thruster would not work and/or the battery voltage cannot be pulled down to 10.6V
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If the thruster voltage does not drop below 10.6V, then there is no problem with the battery or cables.

However, I suspect you will find that the thruster voltage is much lower.
 
PaulRainbow said:
Based on what ?
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That there are cables connecting it to the battery and they have a resistance which is not 0 and that you are drawing current.
That is just physics.
V = IR.

R > 0
I = 100 A or more.
therefore V > 0

So is R small or is it as large as 1 or 2 ohms?
(Cable section size, rust, ....)
 
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